All known communication standards impose limits on the use of system resources, regardless of the type of resources that are allocated. Resource management is used in communication systems to effectively allocate the limited amount of system resources to all users. Such resources may include timeslots, RF carriers or codes. For example, the Universal Mobile Telecommunication System (UMTS) Time Division Duplex (TDD) standards define a single carrier cell that includes a beacon and other common channels and timeslots. Accordingly, in this case, carrier selection is equivalent to cell selection.
In contrast, the China Wireless Telecommunication Standard (CWTS) group Time Division Synchronous Code Division Multiple Access (TD-SCDMA) System for Mobile (TSM) standard defines a multi-carrier cell. However, it requires that all physical channels that belong to a single application be assigned to the same carrier.
A generic multi-carrier TDD system can assign physical resources for a Wireless Transmit/Receive Unit (WTRU) in different timeslots of different carriers. For example, the Fast Dynamic Channel Allocation (F-DCA) algorithm is used to allocate resources (i.e. which timeslots on which carrier) for a user which is referred as a coded composite traffic channel (CCTrCH). This allocation is based on optimization of the assignment quality metric, which can be expressed as a combination of a timeslot-based assignment metric and a fragmentation metric for the whole CCTrCH. In a timeslot-based assignment metric, timeslot interference, timeslot transmit power, or timeslot loading is used. In the fragmentation metric for the whole CCTrCH, a fragmentation penalty of using multiple timeslots within one carrier is assigned, or a fragmentation penalty of using multiple carriers is assigned. Let TS_Frag_Penalty(j) denote the timeslot-based fragmentation penalty when j timeslots are used. For example TS_Frag_Penalty(j) is defined as:
                              TS_Frag          ⁢          _Penalty          ⁢                      (            j            )                          =                  {                                                                      p                  ·                                      (                                          j                      -                      1                                        )                                                                                                                    if                    ⁢                                                                                  ⁢                    0                                    <                  j                  ≤                  C                                                                                    ∞                                                                                                        if                      ⁢                                                                                          ⁢                      j                                        >                    C                                    ;                                                                                        Equation        ⁢                                  ⁢                  (          1          )                    where p is the timeslot-based fragmentation penalty increment, and C is the maximum number of time slots that a user can support.
Let Carrier_Frag_Penalty(j) denote the carrier-based fragmentation penalty when j carriers are used. For example, Carrier_Frag_Penalty(j) is defined as:Carrier—Frag_Penalty(j)=q·(j−1);  Equation (2)where q is the carrier-based fragmentation penalty increment.
Although some WTRUs may use multiple receivers and have no implementation constraints on slot selection, most WTRUs have a single receiver and a finite switching time between uplink (UL) and downlink (DL) timeslots. Therefore, for most WTRUs, when timeslots from more than one carrier are used, the following two limitations apply: 1) if a timeslot is used by the WTRU in one carrier, the same timeslot cannot be used by the WTRU in other carriers; and 2) if a timeslot is used by the WTRU in one carrier, only timeslots that allow enough guard time apart from the used timeslot for the WTRU transceiver to switch frequencies can be used by the same WTRU in other carriers.
Those timeslots that cannot be used because of the usage of a particular timeslot and the two aforementioned limitations are defined as the set of banned timeslots of the particular timeslot.
Although channel allocation algorithms have been developed for TDD systems, these systems typically compromise a single carrier used by an operator. In multi-carrier TDD systems, the network has the freedom to assign the WTRU to one or several carriers. Therefore, there exists a need to properly allocate resources for multi-carrier TDD systems.